1. Technical Field
The present invention relates to an apparatus for making graphic products and, more particularly, to such apparatus for cutting and creasing heavy-weight sheet material.
2. Background Art
A plotting and cutting apparatus is used in the computer generated graphics, sign making and screen printing fields for a variety of purposes. For example, such apparatus is used for cutting graphic images or characters from sheets of vinyl or other polymeric materials, for drawing lines, characters or other graphic images on sheets of paper or polymeric materials, for pounding sheets to form perforated patterns, and for embossing sheets to form embossed patterns.
One type of such apparatus is described in a co-pending U.S. Pat. application Ser. No. 08/826,367, filed Apr. 9, 1997 and assigned to the Assignee of the present invention. The apparatus described in the above-mentioned co-pending patent application has a stationary platen forming a sheet support surface with a worksheet driven over it in a longitudinal direction by a plurality of sprockets. The apparatus also includes a tool supported by a tool carriage allowing lateral movement of the tool. The sheet support surface includes an elongated recess for receiving a low friction and relatively hard support surface. The support surface is in register with the tool such that if the tool is mistakenly driven through the sheet into engagement with the support surface, the tool will penetrate the support surface. For work operations on vinyl-type worksheets, the tool typically penetrates only the top layer and does not penetrate the bottom layer of the worksheet. The vinyl-type worksheets typically include a silicon coated bottom surface which is soft and slippery and does not dull the blade of the tool.
It is desirable to use such plotting and cutting apparatus to fabricate prototype boxes or packages for various products. Typically, the prototype boxes are manufactured from tagboard, cardboard or similar heavyweight sheet material. The prototype boxes are formed by first fabricating a flat blank by cutting around the contour of the box from the sheet material while either completely or substantially severing the flat blank box from the remainder of the sheet material. Typically, a number of tabs connecting the flat blank and the sheet material remain to prevent the blank from separating from the sheet material prior to completion of the operation. Once the contour of the box is cut, the flat blank is creased to form the lines of weakening for subsequent folding.
In order to generate a consistently high precision and quality final product, the cutting operation must yield crisp lines and sharp corners. Such high quality cutting requires the use of a very sharp cutting tool. When the plotting and cutting apparatus described above is used, if the cutting blade cuts through the sheet material and even slightly engages and penetrates the hard sheet support surface, the blade will become dull very quickly. The dull blade losses the ability to produce high quality cuts and to maintain high precision when cutting around the corners of the flat blank. Additionally, the support surface becomes cut and damaged. The cut support surface, which is no longer smooth and includes protruding upwards surfaces, increases friction between the surface and sheet material, thereby inhibiting the motion of the material and the accuracy of the cut.
To further complicate the problem of making high precision, quality prototype boxes, for achieving a good crease in the flat blanks, the sheet material support surface must allow displacement of the sheet material underlying the crease.
Therefore, efficient production of high quality and precision prototype boxes requires two different types of specialized or special purpose support surfaces. One such surface to allow material displacement during creasing of the flat blank and a second support surface allowing complete severing of the flat blank from the sheet material without damaging the support surface or dulling the cutting blade.